This invention relates to auto-focus cameras with photo-electric focus degree measuring means.
It is known to provide a wide variety of types of photo-electric focus degree measuring means in such camera. Of these, the photo-electric focus coincidence detecting mechanism employing the so-called "principle of triangulation" has an important requirement that the two optical system be adjusted in respect to optical axis, as their relative position error leads to a loss in the ability of distance measurement. Moreover, its adjusting mechanism necessitates a fine adjustment so that it tends to be complicated in structure and its adjusting work is very troublesome.
In other words, the conventional triangulation type distance measuring mechanism has the photographic view frame indicating the lens field and the distance measuring area mark indicating the distance measuring field as formed in unison. Thus, there is need of collimating the above-described two optical system in isolation from each other. More concretely speaking, the artisan used first to arrange the photographic field frame within the interior of the finder at an adjusted position with reference to the optical axis of the taking lens, and then to adjust the position of each of the above-described two optical systems, (for example, light projecting optical system and light sensing optical system) with reference to the distance measuring field mark formed in unison with the above-described photographic field frame. However, since, for example, the light projection optical system generally includes means for scanning the light beam, the additional use of the adjusting mechanism for the adjustment of this light projecting optical system calls for difficulties in manufacturing, assembling and adjustment, that is, all the phases of production giving very large disadvantages from the economical and technical standpoints.